GI.Gio.Objects.Subprocess

Subprocess allows the creation of and interaction with child processes.

Processes can be communicated with using standard GIO-style APIs (ie: InputStream, OutputStream). There are GIO-style APIs to wait for process termination (ie: cancellable and with an asynchronous variant).

There is an API to force a process to terminate, as well as a race-free API for sending UNIX signals to a subprocess.

One major advantage that GIO brings over the core GLib library is comprehensive API for asynchronous I/O, such outputStreamSpliceAsync. This makes GSubprocess significantly more powerful and flexible than equivalent APIs in some other languages such as the subprocess.py included with Python. For example, using Subprocess one could create two child processes, reading standard output from the first, processing it, and writing to the input stream of the second, all without blocking the main loop.

A powerful subprocessCommunicate API is provided similar to the communicate() method of subprocess.py. This enables very easy interaction with a subprocess that has been opened with pipes.

Subprocess defaults to tight control over the file descriptors open in the child process, avoiding dangling-fd issues that are caused by a simple fork()/exec(). The only open file descriptors in the spawned process are ones that were explicitly specified by the Subprocess API (unless SubprocessFlagsInheritFds was specified).

Subprocess will quickly reap all child processes as they exit, avoiding "zombie processes" remaining around for long periods of time. subprocessWait can be used to wait for this to happen, but it will happen even without the call being explicitly made.

As a matter of principle, Subprocess has no API that accepts shell-style space-separated strings. It will, however, match the typical shell behaviour of searching the PATH for executables that do not contain a directory separator in their name.

Subprocess attempts to have a very simple API for most uses (ie: spawning a subprocess with arguments and support for most typical kinds of input and output redirection). See g_subprocess_new(). The SubprocessLauncher API is provided for more complicated cases (advanced types of redirection, environment variable manipulation, change of working directory, child setup functions, etc).

A typical use of Subprocess will involve calling g_subprocess_new(), followed by subprocessWaitAsync or subprocessWait. After the process exits, the status can be checked using functions such as subprocessGetIfExited (which are similar to the familiar WIFEXITED-style POSIX macros).

Since: 2.40

Exported types

newtype Subprocess

Memory-managed wrapper type.

Constructors

Subprocess (ManagedPtr Subprocess)

Instances

Eq Subprocess

Defined in GI.Gio.Objects.Subprocess

Methods

(==) :: Subprocess -> Subprocess -> Bool

(/=) :: Subprocess -> Subprocess -> Bool

IsGValue Subprocess

Convert Subprocess to and from GValue with toGValue and fromGValue.

Defined in GI.Gio.Objects.Subprocess

Methods

toGValue :: Subprocess -> IO GValue

fromGValue :: GValue -> IO Subprocess

ManagedPtrNewtype Subprocess

Defined in GI.Gio.Objects.Subprocess

Methods

toManagedPtr :: Subprocess -> ManagedPtr Subprocess

TypedObject Subprocess

Defined in GI.Gio.Objects.Subprocess

Methods

glibType :: IO GType

GObject Subprocess

Defined in GI.Gio.Objects.Subprocess

HasParentTypes Subprocess

Defined in GI.Gio.Objects.Subprocess

type ParentTypes Subprocess

Defined in GI.Gio.Objects.Subprocess

type ParentTypes Subprocess = '[Object, Initable]

class (GObject o, IsDescendantOf Subprocess o) => IsSubprocess o

Type class for types which can be safely cast to Subprocess, for instance with toSubprocess.

Instances

(GObject o, IsDescendantOf Subprocess o) => IsSubprocess o

Defined in GI.Gio.Objects.Subprocess

toSubprocess :: (MonadIO m, IsSubprocess o) => o -> m Subprocess

Cast to Subprocess, for types for which this is known to be safe. For general casts, use castTo.

Methods

Overloaded methods

communicate

subprocessCommunicate

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a, IsCancellable b)

=> a

subprocess: a Subprocess

-> Maybe Bytes

stdinBuf: data to send to the stdin of the subprocess, or Nothing

-> Maybe b

cancellable: a Cancellable

-> m (Maybe Bytes, Maybe Bytes)

(Can throw GError)

Communicate with the subprocess until it terminates, and all input and output has been completed.

If stdinBuf is given, the subprocess must have been created with SubprocessFlagsStdinPipe. The given data is fed to the stdin of the subprocess and the pipe is closed (ie: EOF).

At the same time (as not to cause blocking when dealing with large amounts of data), if SubprocessFlagsStdoutPipe or SubprocessFlagsStderrPipe were used, reads from those streams. The data that was read is returned in stdout and/or the stderr.

If the subprocess was created with SubprocessFlagsStdoutPipe, stdoutBuf will contain the data read from stdout. Otherwise, for subprocesses not created with SubprocessFlagsStdoutPipe, stdoutBuf will be set to Nothing. Similar provisions apply to stderrBuf and SubprocessFlagsStderrPipe.

As usual, any output variable may be given as Nothing to ignore it.

If you desire the stdout and stderr data to be interleaved, create the subprocess with SubprocessFlagsStdoutPipe and SubprocessFlagsStderrMerge. The merged result will be returned in stdoutBuf and stderrBuf will be set to Nothing.

In case of any error (including cancellation), False will be returned with error set. Some or all of the stdin data may have been written. Any stdout or stderr data that has been read will be discarded. None of the out variables (aside from error) will have been set to anything in particular and should not be inspected.

In the case that True is returned, the subprocess has exited and the exit status inspection APIs (eg: subprocessGetIfExited, subprocessGetExitStatus) may be used.

You should not attempt to use any of the subprocess pipes after starting this function, since they may be left in strange states, even if the operation was cancelled. You should especially not attempt to interact with the pipes while the operation is in progress (either from another thread or if using the asynchronous version).

Since: 2.40

communicateAsync

subprocessCommunicateAsync

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a, IsCancellable b)

=> a

subprocess: Self

-> Maybe Bytes

stdinBuf: Input data, or Nothing

-> Maybe b

cancellable: Cancellable

-> Maybe AsyncReadyCallback

callback: Callback

-> m ()

Asynchronous version of subprocessCommunicate. Complete invocation with subprocessCommunicateFinish.

communicateFinish

subprocessCommunicateFinish

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a, IsAsyncResult b)

=> a

subprocess: Self

-> b

result: Result

-> m (Maybe Bytes, Maybe Bytes)

(Can throw GError)

Complete an invocation of subprocessCommunicateAsync.

communicateUtf8

subprocessCommunicateUtf8

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a, IsCancellable b)

=> a

subprocess: a Subprocess

-> Maybe Text

stdinBuf: data to send to the stdin of the subprocess, or Nothing

-> Maybe b

cancellable: a Cancellable

-> m (Maybe Text, Maybe Text)

(Can throw GError)

Like subprocessCommunicate, but validates the output of the process as UTF-8, and returns it as a regular NUL terminated string.

On error, stdoutBuf and stderrBuf will be set to undefined values and should not be used.

communicateUtf8Async

subprocessCommunicateUtf8Async

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a, IsCancellable b)

=> a

subprocess: Self

-> Maybe Text

stdinBuf: Input data, or Nothing

-> Maybe b

cancellable: Cancellable

-> Maybe AsyncReadyCallback

callback: Callback

-> m ()

Asynchronous version of subprocessCommunicateUtf8. Complete invocation with subprocessCommunicateUtf8Finish.

communicateUtf8Finish

subprocessCommunicateUtf8Finish

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a, IsAsyncResult b)

=> a

subprocess: Self

-> b

result: Result

-> m (Maybe Text, Maybe Text)

(Can throw GError)

Complete an invocation of subprocessCommunicateUtf8Async.

forceExit

subprocessForceExit

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a)

=> a

subprocess: a Subprocess

-> m ()

Use an operating-system specific method to attempt an immediate, forceful termination of the process. There is no mechanism to determine whether or not the request itself was successful; however, you can use subprocessWait to monitor the status of the process after calling this function.

On Unix, this function sends SIGKILL.

Since: 2.40

getExitStatus

subprocessGetExitStatus

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a)

=> a

subprocess: a Subprocess

-> m Int32

Returns: the exit status

Check the exit status of the subprocess, given that it exited normally. This is the value passed to the exit() system call or the return value from main.

This is equivalent to the system WEXITSTATUS macro.

It is an error to call this function before subprocessWait and unless subprocessGetIfExited returned True.

Since: 2.40

getIdentifier

subprocessGetIdentifier

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a)

=> a

subprocess: a Subprocess

-> m (Maybe Text)

Returns: the subprocess identifier, or Nothing if the subprocess has terminated

On UNIX, returns the process ID as a decimal string. On Windows, returns the result of GetProcessId() also as a string. If the subprocess has terminated, this will return Nothing.

Since: 2.40

getIfExited

subprocessGetIfExited

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a)

=> a

subprocess: a Subprocess

-> m Bool

Returns: True if the case of a normal exit

Check if the given subprocess exited normally (ie: by way of exit() or return from main()).

This is equivalent to the system WIFEXITED macro.

It is an error to call this function before subprocessWait has returned.

Since: 2.40

getIfSignaled

subprocessGetIfSignaled

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a)

=> a

subprocess: a Subprocess

-> m Bool

Returns: True if the case of termination due to a signal

Check if the given subprocess terminated in response to a signal.

This is equivalent to the system WIFSIGNALED macro.

It is an error to call this function before subprocessWait has returned.

Since: 2.40

getStatus

subprocessGetStatus

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a)

=> a

subprocess: a Subprocess

-> m Int32

Returns: the (meaningless) waitpid() exit status from the kernel

Gets the raw status code of the process, as from waitpid().

This value has no particular meaning, but it can be used with the macros defined by the system headers such as WIFEXITED. It can also be used with spawnCheckExitStatus.

It is more likely that you want to use subprocessGetIfExited followed by subprocessGetExitStatus.

It is an error to call this function before subprocessWait has returned.

Since: 2.40

getStderrPipe

subprocessGetStderrPipe

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a)

=> a

subprocess: a Subprocess

-> m InputStream

Returns: the stderr pipe

Gets the InputStream from which to read the stderr output of subprocess.

The process must have been created with SubprocessFlagsStderrPipe.

Since: 2.40

getStdinPipe

subprocessGetStdinPipe

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a)

=> a

subprocess: a Subprocess

-> m OutputStream

Returns: the stdout pipe

Gets the OutputStream that you can write to in order to give data to the stdin of subprocess.

The process must have been created with SubprocessFlagsStdinPipe.

Since: 2.40

getStdoutPipe

subprocessGetStdoutPipe

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a)

=> a

subprocess: a Subprocess

-> m InputStream

Returns: the stdout pipe

Gets the InputStream from which to read the stdout output of subprocess.

The process must have been created with SubprocessFlagsStdoutPipe.

Since: 2.40

getSuccessful

subprocessGetSuccessful

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a)

=> a

subprocess: a Subprocess

-> m Bool

Returns: True if the process exited cleanly with a exit status of 0

Checks if the process was "successful". A process is considered successful if it exited cleanly with an exit status of 0, either by way of the exit() system call or return from main().

It is an error to call this function before subprocessWait has returned.

Since: 2.40

getTermSig

subprocessGetTermSig

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a)

=> a

subprocess: a Subprocess

-> m Int32

Returns: the signal causing termination

Get the signal number that caused the subprocess to terminate, given that it terminated due to a signal.

This is equivalent to the system WTERMSIG macro.

It is an error to call this function before subprocessWait and unless subprocessGetIfSignaled returned True.

Since: 2.40

new

subprocessNew

Arguments

:: (HasCallStack, MonadIO m)

=> [[Char]]

argv: commandline arguments for the subprocess

-> [SubprocessFlags]

flags: flags that define the behaviour of the subprocess

-> m Subprocess

Returns: A newly created Subprocess, or Nothing on error (and error will be set) (Can throw GError)

Create a new process with the given flags and argument list.

The argument list is expected to be Nothing-terminated.

Since: 2.40

sendSignal

subprocessSendSignal

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a)

=> a

subprocess: a Subprocess

-> Int32

signalNum: the signal number to send

-> m ()

Sends the UNIX signal signalNum to the subprocess, if it is still running.

This API is race-free. If the subprocess has terminated, it will not be signalled.

This API is not available on Windows.

Since: 2.40

wait

subprocessWait

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a, IsCancellable b)

=> a

subprocess: a Subprocess

-> Maybe b

cancellable: a Cancellable

-> m ()

(Can throw GError)

Synchronously wait for the subprocess to terminate.

After the process terminates you can query its exit status with functions such as subprocessGetIfExited and subprocessGetExitStatus.

This function does not fail in the case of the subprocess having abnormal termination. See subprocessWaitCheck for that.

Cancelling cancellable doesn't kill the subprocess. Call subprocessForceExit if it is desirable.

Since: 2.40

waitAsync

subprocessWaitAsync

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a, IsCancellable b)

=> a

subprocess: a Subprocess

-> Maybe b

cancellable: a Cancellable, or Nothing

-> Maybe AsyncReadyCallback

callback: a AsyncReadyCallback to call when the operation is complete

-> m ()

Wait for the subprocess to terminate.

This is the asynchronous version of subprocessWait.

Since: 2.40

waitCheck

subprocessWaitCheck

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a, IsCancellable b)

=> a

subprocess: a Subprocess

-> Maybe b

cancellable: a Cancellable

-> m ()

(Can throw GError)

Combines subprocessWait with spawnCheckExitStatus.

Since: 2.40

waitCheckAsync

subprocessWaitCheckAsync

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a, IsCancellable b)

=> a

subprocess: a Subprocess

-> Maybe b

cancellable: a Cancellable, or Nothing

-> Maybe AsyncReadyCallback

callback: a AsyncReadyCallback to call when the operation is complete

-> m ()

Combines subprocessWaitAsync with spawnCheckExitStatus.

This is the asynchronous version of subprocessWaitCheck.

Since: 2.40

waitCheckFinish

subprocessWaitCheckFinish

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a, IsAsyncResult b)

=> a

subprocess: a Subprocess

-> b

result: the AsyncResult passed to your AsyncReadyCallback

-> m ()

(Can throw GError)

Collects the result of a previous call to subprocessWaitCheckAsync.

Since: 2.40

waitFinish

subprocessWaitFinish

Arguments

:: (HasCallStack, MonadIO m, IsSubprocess a, IsAsyncResult b)

=> a

subprocess: a Subprocess

-> b

result: the AsyncResult passed to your AsyncReadyCallback

-> m ()

(Can throw GError)

Collects the result of a previous call to subprocessWaitAsync.

Since: 2.40

Properties

argv

No description available in the introspection data.

constructSubprocessArgv :: (IsSubprocess o, MonadIO m) => [Text] -> m (GValueConstruct o)

Construct a GValueConstruct with valid value for the “argv” property. This is rarely needed directly, but it is used by new.

flags

No description available in the introspection data.

constructSubprocessFlags :: (IsSubprocess o, MonadIO m) => [SubprocessFlags] -> m (GValueConstruct o)

Construct a GValueConstruct with valid value for the “flags” property. This is rarely needed directly, but it is used by new.